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Investigation Into the effect of Temperature on Respiration

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Introduction

Investigation Into the effect of Temperature on Respiration Scientific Knowledge 'Respiration is the process in which organic molecules act as fuel' (from Central concepts by Mary Jones and Jennifer Gregory). Respiration is needed to produce ATP. ATP is an immediate and universal state of energy for cells. It is made available for use in the living cell by respiration. Respiration takes place in the mitochondria in the cell. A series of oxidation and reduction reactions take place, in which respiratory substrates (glucose is the major respiratory substrate) are oxidised to carbon dioxide, and oxygen reduced to water. You can measure the rate of respiration by collecting carbon dioxide. Here is an explanation of respiration to show why this method can be used. Glucose is a relatively large molecule containing six carbon atoms, all in reduced state. During respiration glucose undergoes a series of enzymes catalysed oxidation reactions. These reactions occur in three main stages: Glycolysis, the Krebs cycle and the electron transfer chain. 'Glycolysis is a series of reactions in which six-carbon sugar is broken down to two molecules of the three-carbon pyvurate ion' (from Advanced Biology by John Murray). The process of glycolysis are common to both anaerobic and aerobic respiration. After glycolysis takes place, the product pyvurate enters the mitochondria. It is then decarboxylated (by removal of carbon dioxide). The two remaining carbons react with coenzyme A to form acetylcoenzyme. Simultaneously hydrogen ions are transferred to the hydrogen acceptor NAD, which forms NADH. ...read more.

Middle

The faster moving molecules collide more often therefore increasing rate of reaction. As the temperature continues to increase, the enzyme molecules begin to vibrate vigorously. This breaks the hydrogen bonds and other bonds holding the enzyme I its precise shape. The enzyme therefore changes shape and becomes denatured. The substrate can no longer fit into active site because the active site has changed. The enzyme loses its ability to catalyse the reaction and becomes ineffective. The rate of reaction slows as the temperature increases and finally will stop if the temperature continues to rise. The optimum temperature for an enzyme varies depending on environment it acts in. In this experiment, temperature will be used as the variable. Temperature is easier to measure the change in temperature more accurately than the other variables. pH Hydrogen bonding is responsible for holding the precise three-dimensional shape of the enzyme. pH is the measure of concentration of hydrogen ions. These bonds may be broken by the concentration of hydrogen ions. By breaking the bonds because of any change in pH Will effectively denature the enzymes. Each enzyme works best at a particular pH . Deviations from this will cause denaturation. Denaturation would decrease rate of reaction and then finally stop the reaction all together. The pH can be maintained by using a buffer solution for each sample. Prediction I predict that the rate of reaction will double every time the temperature increases by 10. ...read more.

Conclusion

Five different temperatures will be taken to see how the rate of respiration is affected in a range of temperatures. Three repeats will be done so a mean result can be obtained. This will help produce a more accurate mean. Diagram as in Pilot Study. 1. Begin to heat water bath using Bunsen burner. 2. Heat temperature of 20,30,40,50,60,70 . 3. Measure out 20cm of yeast and glucose solution (1g dried yeast and 3g of glucose dissolved in 100 cm of water) into boiling tube and leave in test tube rack. 4. To help keep the experiment a fair test, measure out 20cm of yeast and glucose solution in each boiling tube. 5. Heat water bath until at correct temperature 6. Then add boiling tubes of yeast and glucose solution. 7. Leave to acclimatise and reach temperature before collecting gas. 8. Leave for set amount of time long enough to gain significant gas production for analyse. (10 mins) 9. Measure amount of gas produced by how much water has been displaced from graduated measuring cylinder. 10. To ensure validity of reading, make sure you n=measure the graduated test tube at eye level on a flat surface. Risk Assessment * Use extreme caution when using the Bunsen burner as flame could cause harm. * Tuck in tie so it does not interfere with experiment e.g get caught in the flame * Wear goggles to protect from eye damage * Use gloves when removing water bath from gauze so as not to burn yourself. * Use tongs to lift hot boiling tubes from water bath. . . ...read more.

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